newlib/libc/string/strlcat.c

   1 /*      $OpenBSD: strlcat.c,v 1.19 2019/01/25 00:19:25 millert Exp $    */
   2
   3 /*
   4  * Copyright (c) 1998, 2015 Todd C. Miller <millert@openbsd.org>
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include <sys/types.h>
  20 #include <string.h>
  21
  22 /*
  23  * Appends src to string dst of size dsize (unlike strncat, dsize is the
  24  * full size of dst, not space left).  At most dsize-1 characters
  25  * will be copied.  Always NUL terminates (unless dsize <= strlen(dst)).
  26  * Returns strlen(src) + MIN(dsize, strlen(initial dst)).
  27  * If retval >= dsize, truncation occurred.
  28  */
  29 size_t
  30 strlcat (char *dst,
  31          const char *src,
  32          size_t dsize)
  33 {
  34         const char *odst = dst;
  35         const char *osrc = src;
  36         size_t n = dsize;
  37         size_t dlen;
  38
  39         /* Find the end of dst and adjust bytes left but don't go past end. */
  40         while (n-- != 0 && *dst != '\0')
  41                 dst++;
  42         dlen = dst - odst;
  43         n = dsize - dlen;
  44
  45         if (n-- == 0)
  46                 return(dlen + strlen(src));
  47         while (*src != '\0') {
  48                 if (n != 0) {
  49                         *dst++ = *src;
  50                         n--;
  51                 }
  52                 src++;
  53         }
  54         *dst = '\0';
  55
  56         return(dlen + (src - osrc));    /* count does not include NUL */
  57 }